<!DOCTYPE html>



  


<html class="theme-next pisces use-motion" lang="en">
<head><meta name="generator" content="Hexo 3.8.0">
  <meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<meta name="theme-color" content="#222">









<meta http-equiv="Cache-Control" content="no-transform">
<meta http-equiv="Cache-Control" content="no-siteapp">















  
  
  <link href="/lib/fancybox/source/jquery.fancybox.css?v=2.1.5" rel="stylesheet" type="text/css">




  
  
  
  

  
    
    
  

  

  

  

  

  
    
    
    <link href="//fonts.googleapis.com/css?family=Lato:300,300italic,400,400italic,700,700italic&subset=latin,latin-ext" rel="stylesheet" type="text/css">
  






<link href="/lib/font-awesome/css/font-awesome.min.css?v=4.6.2" rel="stylesheet" type="text/css">

<link href="/css/main.css?v=5.1.2" rel="stylesheet" type="text/css">


  <meta name="keywords" content="ML,DS,">





  <link rel="alternate" href="/atom.xml" title="Hero's notebooks" type="application/atom+xml">




  <link rel="shortcut icon" type="image/x-icon" href="/favicon.ico?v=5.1.2">






<meta name="description" content="贪心算法顾名思义，贪心算法总是作出在当前看来最好的选择。也就是说贪心算法并不从整体最优考虑，它所作出的选择只是在某种意义上的局部最优选择。在一些情况下，即使贪心算法不能得到整体最优解，其最终结果却是最优解的很好近似。  贪心选择性质。所谓贪心选择性质是指所求问题的整体最优解可以通过一系列局部最优的选择，即贪心选择来达到。这是贪心算法可行的第一个基本要素，也是贪心算法与动态规划算法的主要区别。 动态">
<meta name="keywords" content="ML,DS">
<meta property="og:type" content="article">
<meta property="og:title" content="贪心算法">
<meta property="og:url" content="https://chenzk1.github.io/2019/11/19/贪心算法/index.html">
<meta property="og:site_name" content="Hero&#39;s notebooks">
<meta property="og:description" content="贪心算法顾名思义，贪心算法总是作出在当前看来最好的选择。也就是说贪心算法并不从整体最优考虑，它所作出的选择只是在某种意义上的局部最优选择。在一些情况下，即使贪心算法不能得到整体最优解，其最终结果却是最优解的很好近似。  贪心选择性质。所谓贪心选择性质是指所求问题的整体最优解可以通过一系列局部最优的选择，即贪心选择来达到。这是贪心算法可行的第一个基本要素，也是贪心算法与动态规划算法的主要区别。 动态">
<meta property="og:locale" content="en">
<meta property="og:image" content="https://img-my.csdn.net/uploads/201303/29/1364554174_8902.jpg">
<meta property="og:image" content="https://img-my.csdn.net/uploads/201303/30/1364630415_9404.jpg">
<meta property="og:updated_time" content="2019-11-19T02:27:50.033Z">
<meta name="twitter:card" content="summary">
<meta name="twitter:title" content="贪心算法">
<meta name="twitter:description" content="贪心算法顾名思义，贪心算法总是作出在当前看来最好的选择。也就是说贪心算法并不从整体最优考虑，它所作出的选择只是在某种意义上的局部最优选择。在一些情况下，即使贪心算法不能得到整体最优解，其最终结果却是最优解的很好近似。  贪心选择性质。所谓贪心选择性质是指所求问题的整体最优解可以通过一系列局部最优的选择，即贪心选择来达到。这是贪心算法可行的第一个基本要素，也是贪心算法与动态规划算法的主要区别。 动态">
<meta name="twitter:image" content="https://img-my.csdn.net/uploads/201303/29/1364554174_8902.jpg">



<script type="text/javascript" id="hexo.configurations">
  var NexT = window.NexT || {};
  var CONFIG = {
    root: '/',
    scheme: 'Pisces',
    sidebar: {"position":"left","display":"post","offset":12,"offset_float":12,"b2t":false,"scrollpercent":false,"onmobile":false},
    fancybox: true,
    tabs: true,
    motion: true,
    duoshuo: {
      userId: '0',
      author: 'Author'
    },
    algolia: {
      applicationID: '',
      apiKey: '',
      indexName: '',
      hits: {"per_page":10},
      labels: {"input_placeholder":"Search for Posts","hits_empty":"We didn't find any results for the search: ${query}","hits_stats":"${hits} results found in ${time} ms"}
    }
  };
</script>



  <link rel="canonical" href="https://chenzk1.github.io/2019/11/19/贪心算法/">





  <title>贪心算法 | Hero's notebooks</title>
  














</head>

<body itemscope itemtype="http://schema.org/WebPage" lang="en">

  
  
    
  

  <div class="container sidebar-position-left page-post-detail ">
    <div class="headband"></div>

    <header id="header" class="header" itemscope itemtype="http://schema.org/WPHeader">
      <div class="header-inner"><div class="site-brand-wrapper">
  <div class="site-meta ">
    

    <div class="custom-logo-site-title">
      <a href="/" class="brand" rel="start">
        <span class="logo-line-before"><i></i></span>
        <span class="site-title">Hero's notebooks</span>
        <span class="logo-line-after"><i></i></span>
      </a>
    </div>
      
        <p class="site-subtitle">Sometimes naive.</p>
      
  </div>

  <div class="site-nav-toggle">
    <button>
      <span class="btn-bar"></span>
      <span class="btn-bar"></span>
      <span class="btn-bar"></span>
    </button>
  </div>
</div>

<nav class="site-nav">
  

  
    <ul id="menu" class="menu">
      
        
        <li class="menu-item menu-item-home">
          <a href="/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-home"></i> <br>
            
            Home
          </a>
        </li>
      
        
        <li class="menu-item menu-item-archives">
          <a href="/archives/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-archive"></i> <br>
            
            Archives
          </a>
        </li>
      
        
        <li class="menu-item menu-item-tags">
          <a href="/tags/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-tags"></i> <br>
            
            Tags
          </a>
        </li>
      
        
        <li class="menu-item menu-item-categories">
          <a href="/categories/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-th"></i> <br>
            
            Categories
          </a>
        </li>
      

      
        <li class="menu-item menu-item-search">
          
            <a href="javascript:;" class="popup-trigger">
          
            
              <i class="menu-item-icon fa fa-search fa-fw"></i> <br>
            
            Search
          </a>
        </li>
      
    </ul>
  

  
    <div class="site-search">
      
  <div class="popup search-popup local-search-popup">
  <div class="local-search-header clearfix">
    <span class="search-icon">
      <i class="fa fa-search"></i>
    </span>
    <span class="popup-btn-close">
      <i class="fa fa-times-circle"></i>
    </span>
    <div class="local-search-input-wrapper">
      <input autocomplete="off" placeholder="Searching..." spellcheck="false" type="text" id="local-search-input">
    </div>
  </div>
  <div id="local-search-result"></div>
</div>



    </div>
  
</nav>



 </div>
    </header>

    <main id="main" class="main">
      <div class="main-inner">
        <div class="content-wrap">
          <div id="content" class="content">
            

  <div id="posts" class="posts-expand">
    

  

  
  
  

  <article class="post post-type-normal" itemscope itemtype="http://schema.org/Article">
  
  
  
  <div class="post-block">
    <link itemprop="mainEntityOfPage" href="https://chenzk1.github.io/2019/11/19/贪心算法/">

    <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
      <meta itemprop="name" content="Hero">
      <meta itemprop="description" content>
      <meta itemprop="image" content="/images/avatar.jpg">
    </span>

    <span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
      <meta itemprop="name" content="Hero's notebooks">
    </span>

    
      <header class="post-header">

        
        
          <h1 class="post-title" itemprop="name headline">贪心算法</h1>
        

        <div class="post-meta">
          <span class="post-time">
            
              <span class="post-meta-item-icon">
                <i class="fa fa-calendar-o"></i>
              </span>
              
                <span class="post-meta-item-text">Posted on</span>
              
              <time title="Post created" itemprop="dateCreated datePublished" datetime="2019-11-19T10:23:10+08:00">
                2019-11-19
              </time>
            

            

            
          </span>

          
            <span class="post-category">
            
              <span class="post-meta-divider">|</span>
            
              <span class="post-meta-item-icon">
                <i class="fa fa-folder-o"></i>
              </span>
              
                <span class="post-meta-item-text">In</span>
              
              
                <span itemprop="about" itemscope itemtype="http://schema.org/Thing">
                  <a href="/categories/Learning/" itemprop="url" rel="index">
                    <span itemprop="name">Learning</span>
                  </a>
                </span>

                
                
              
            </span>
          

          
            
          

          
          

          

          

          

        </div>
      </header>
    

    
    
    
    <div class="post-body" itemprop="articleBody">

      
      

      
        <h4 id="贪心算法"><a href="#贪心算法" class="headerlink" title="贪心算法"></a>贪心算法</h4><p>顾名思义，贪心算法总是作出在当前看来最好的选择。也就是说贪心算法并不从整体最优考虑，它所作出的选择只是在某种意义上的局部最优选择。在一些情况下，即使贪心算法不能得到整体最优解，其最终结果却是最优解的很好近似。</p>
<ul>
<li><p>贪心选择性质。所谓贪心选择性质是指所求问题的整体最优解可以通过一系列局部最优的选择，即贪心选择来达到。这是贪心算法可行的第一个基本要素，也是贪心算法与动态规划算法的主要区别。</p>
<p>动态规划算法通常以自底向上的方式解各子问题，而贪心算法则通常以自顶向下的方式进行，以迭代的方式作出相继的贪心选择，每作一次贪心选择就将所求问题简化为规模更小的子问题。</p>
<p>对于一个具体问题，要确定它是否具有贪心选择性质，必须证明每一步所作的贪心选择最终导致问题的整体最优解。</p>
</li>
<li><p>当一个问题的最优解包含其子问题的最优解时，称此问题具有最优子结构性质。问题的最优子结构性质是该问题可用动态规划算法或贪心算法求解的关键特征。</p>
</li>
</ul>
<h4 id="活动时间安排"><a href="#活动时间安排" class="headerlink" title="活动时间安排"></a>活动时间安排</h4><p>设有N个活动时间集合，每个活动都要使用同一个资源，比如说会议场，而且同一时间内只能有一个活动使用，每个活动都有一个使用活动的开始si和结束时间fi，即他的使用区间为（si,fi）,现在要求你分配活动占用时间表，即哪些活动占用该会议室，哪些不占用，使得他们不冲突，要求是尽可能多的使参加的活动最大化，即所占时间区间最大化。</p>
<p><img src="https://img-my.csdn.net/uploads/201303/29/1364554174_8902.jpg" alt="img"></p>
<ul>
<li>重点：<strong>结束时间按顺序排列</strong>。时间从前往后推移，若以当时时间为开始时间的活动的开始时间≥前一个活动的结束时间，选择此活动即可 –&gt; 原因是<strong>结束时间按顺序排列</strong>。</li>
</ul>
<figure class="highlight plain"><figcaption><span>main(int argc, char* argv[])</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line">int main(int argc,char* argv[])</span><br><span class="line">&#123;</span><br><span class="line">	int s[11] =&#123;1,3,0,5,3,5,6,8,8,2,12&#125;;</span><br><span class="line">	int f[11] =&#123;4,5,6,7,8,9,10,11,12,13,14&#125;;</span><br><span class="line"> </span><br><span class="line">	bool mark[11] = &#123;0&#125;;</span><br><span class="line"> </span><br><span class="line">	GreedyChoose(11,s,f,mark);</span><br><span class="line">	for(int i=0;i&lt;11;i++)</span><br><span class="line">		if(mark[i])</span><br><span class="line">			cout&lt;&lt;i&lt;&lt;&quot; &quot;;</span><br><span class="line">	system(&quot;pause&quot;);</span><br><span class="line">	return 0;</span><br><span class="line">&#125;</span><br><span class="line"> </span><br><span class="line">void GreedyChoose(int len,int *s,int *f,bool *flag)</span><br><span class="line">&#123;</span><br><span class="line">	flag[0] = true;</span><br><span class="line">	int j = 0;</span><br><span class="line">	for(int i=1;i&lt;len;++i)</span><br><span class="line">		if(s[i] &gt;= f[j])</span><br><span class="line">		&#123;</span><br><span class="line">			flag[i] = true;</span><br><span class="line">			j = i;</span><br><span class="line">		&#125;</span><br></pre></td></tr></table></figure>
<h4 id="线段覆盖"><a href="#线段覆盖" class="headerlink" title="线段覆盖"></a>线段覆盖</h4><p>在一维空间中告诉你N条线段的起始坐标与终止坐标，要求求出这些线段一共覆盖了多大的长度。</p>
<p><img src="https://img-my.csdn.net/uploads/201303/30/1364630415_9404.jpg" alt="img"></p>
<p>重点：<strong>将线段按起始坐标排序</strong>。</p>
<figure class="highlight plain"><figcaption><span>main(int argc, char* argv[])</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line">&#123;</span><br><span class="line">	int s[10] = &#123;2,3,4,5,6,7,8,9,10,11&#125;;</span><br><span class="line">	int f[10] = &#123;3,5,7,6,9,8,12,10,13,15&#125;;</span><br><span class="line">	int TotalLength = (3-2);                 </span><br><span class="line"> </span><br><span class="line">	for(int i=1,int j=0; i&lt;10 ; ++i)</span><br><span class="line">	&#123;</span><br><span class="line">		if(s[i] &gt;= f[j])</span><br><span class="line">		&#123;</span><br><span class="line">			TotalLength += (f[i]-s[i]);</span><br><span class="line">			j = i;</span><br><span class="line">		&#125;</span><br><span class="line">		else</span><br><span class="line">		&#123;</span><br><span class="line">			if(f[i] &lt;= f[j])</span><br><span class="line">				continue;</span><br><span class="line">			else</span><br><span class="line">			&#123;</span><br><span class="line">				TotalLength += f[i] - f[j];</span><br><span class="line">				j = i;</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line"> </span><br><span class="line">	cout&lt;&lt;TotalLength&lt;&lt;endl;</span><br><span class="line">	system(&quot;pause&quot;);</span><br><span class="line">	return 0;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h4 id="找零钱问题"><a href="#找零钱问题" class="headerlink" title="找零钱问题"></a>找零钱问题</h4><p>贪心：每次选择可选的最大面值的钱。</p>
<p>本质上还是<strong>排序</strong>。</p>
<h4 id="Leetcode"><a href="#Leetcode" class="headerlink" title="Leetcode:"></a>Leetcode:</h4><p>给定一个数组，它的第 <em>i</em> 个元素是一支给定股票第 <em>i</em> 天的价格。</p>
<p>设计一个算法来计算你所能获取的最大利润。你可以尽可能地完成更多的交易（多次买卖一支股票）。</p>
<p><strong>注意：</strong>你不能同时参与多笔交易（你必须在再次购买前出售掉之前的股票）。</p>
<p><a href="https://leetcode-cn.com/explore/interview/card/top-interview-questions-easy/1/array/22/" target="_blank" rel="noopener">https://leetcode-cn.com/explore/interview/card/top-interview-questions-easy/1/array/22/</a></p>
<p>使用贪心算法的一个假设：同一天可以卖出又可以买入</p>
<figure class="highlight plain"><figcaption><span>Solution</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">def maxProfit(self, prices: List[int]) -&gt; int:</span><br><span class="line">    ans = 0</span><br><span class="line">    for i in range(len(prices)-1):</span><br><span class="line">        if prices[i+1]&gt;prices[i]:</span><br><span class="line">            ans += prices[i+1]-prices[i]</span><br><span class="line">    return ans</span><br></pre></td></tr></table></figure>

      
    </div>
    
    
    

    

    

    

    <footer class="post-footer">
      
        <div class="post-tags">
          
            <a href="/tags/ML/" rel="tag"># ML</a>
          
            <a href="/tags/DS/" rel="tag"># DS</a>
          
        </div>
      

      
      
      

      
        <div class="post-nav">
          <div class="post-nav-next post-nav-item">
            
              <a href="/2019/11/19/评分卡优化/" rel="next" title="评分卡优化">
                <i class="fa fa-chevron-left"></i> 评分卡优化
              </a>
            
          </div>

          <span class="post-nav-divider"></span>

          <div class="post-nav-prev post-nav-item">
            
              <a href="/2019/11/19/滴滴实习总结/" rel="prev" title="滴滴实习总结">
                滴滴实习总结 <i class="fa fa-chevron-right"></i>
              </a>
            
          </div>
        </div>
      

      
      
    </footer>
  </div>
  
  
  
  </article>



    <div class="post-spread">
      
    </div>
  </div>


          </div>
          


          
  <div class="comments" id="comments">
    
  </div>


        </div>
        
          
  
  <div class="sidebar-toggle">
    <div class="sidebar-toggle-line-wrap">
      <span class="sidebar-toggle-line sidebar-toggle-line-first"></span>
      <span class="sidebar-toggle-line sidebar-toggle-line-middle"></span>
      <span class="sidebar-toggle-line sidebar-toggle-line-last"></span>
    </div>
  </div>

  <aside id="sidebar" class="sidebar">
    
    <div class="sidebar-inner">

      

      
        <ul class="sidebar-nav motion-element">
          <li class="sidebar-nav-toc sidebar-nav-active" data-target="post-toc-wrap">
            Table of Contents
          </li>
          <li class="sidebar-nav-overview" data-target="site-overview">
            Overview
          </li>
        </ul>
      

      <section class="site-overview sidebar-panel">
        <div class="site-author motion-element" itemprop="author" itemscope itemtype="http://schema.org/Person">
          <img class="site-author-image" itemprop="image" src="/images/avatar.jpg" alt="Hero">
          <p class="site-author-name" itemprop="name">Hero</p>
           
              <p class="site-description motion-element" itemprop="description">hero's notebooks</p>
          
        </div>
        <nav class="site-state motion-element">

          
            <div class="site-state-item site-state-posts">
              <a href="/archives/">
                <span class="site-state-item-count">47</span>
                <span class="site-state-item-name">posts</span>
              </a>
            </div>
          

          
            
            
            <div class="site-state-item site-state-categories">
              <a href="/categories/index.html">
                <span class="site-state-item-count">1</span>
                <span class="site-state-item-name">categories</span>
              </a>
            </div>
          

          
            
            
            <div class="site-state-item site-state-tags">
              <a href="/tags/index.html">
                <span class="site-state-item-count">26</span>
                <span class="site-state-item-name">tags</span>
              </a>
            </div>
          

        </nav>

        
          <div class="feed-link motion-element">
            <a href="/atom.xml" rel="alternate">
              <i class="fa fa-rss"></i>
              RSS
            </a>
          </div>
        

        <div class="links-of-author motion-element">
          
        </div>

        
        

        
        

        


      </section>

      
      <!--noindex-->
        <section class="post-toc-wrap motion-element sidebar-panel sidebar-panel-active">
          <div class="post-toc">

            
              
            

            
              <div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-4"><a class="nav-link" href="#贪心算法"><span class="nav-number">1.</span> <span class="nav-text">贪心算法</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#活动时间安排"><span class="nav-number">2.</span> <span class="nav-text">活动时间安排</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#线段覆盖"><span class="nav-number">3.</span> <span class="nav-text">线段覆盖</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#找零钱问题"><span class="nav-number">4.</span> <span class="nav-text">找零钱问题</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#Leetcode"><span class="nav-number">5.</span> <span class="nav-text">Leetcode:</span></a></li></ol></div>
            

          </div>
        </section>
      <!--/noindex-->
      

      

    </div>
  </aside>


        
      </div>
    </main>

    <footer id="footer" class="footer">
      <div class="footer-inner">
        <div class="copyright">
  
  &copy; 
  <span itemprop="copyrightYear">2019</span>
  <span class="with-love">
    <i class="fa fa-heart"></i>
  </span>
  <span class="author" itemprop="copyrightHolder">Hero</span>
</div>


<div class="powered-by">
  Powered by <a class="theme-link" href="https://hexo.io">Hexo</a>
</div>

<div class="theme-info">
  Theme -
  <a class="theme-link" href="https://github.com/iissnan/hexo-theme-next">
    NexT.Pisces
  </a>
</div>


        

        
      </div>
    </footer>

    
      <div class="back-to-top">
        <i class="fa fa-arrow-up"></i>
        
      </div>
    

  </div>

  

<script type="text/javascript">
  if (Object.prototype.toString.call(window.Promise) !== '[object Function]') {
    window.Promise = null;
  }
</script>









  












  
  <script type="text/javascript" src="/lib/jquery/index.js?v=2.1.3"></script>

  
  <script type="text/javascript" src="/lib/fastclick/lib/fastclick.min.js?v=1.0.6"></script>

  
  <script type="text/javascript" src="/lib/jquery_lazyload/jquery.lazyload.js?v=1.9.7"></script>

  
  <script type="text/javascript" src="/lib/velocity/velocity.min.js?v=1.2.1"></script>

  
  <script type="text/javascript" src="/lib/velocity/velocity.ui.min.js?v=1.2.1"></script>

  
  <script type="text/javascript" src="/lib/fancybox/source/jquery.fancybox.pack.js?v=2.1.5"></script>


  


  <script type="text/javascript" src="/js/src/utils.js?v=5.1.2"></script>

  <script type="text/javascript" src="/js/src/motion.js?v=5.1.2"></script>



  
  


  <script type="text/javascript" src="/js/src/affix.js?v=5.1.2"></script>

  <script type="text/javascript" src="/js/src/schemes/pisces.js?v=5.1.2"></script>



  
  <script type="text/javascript" src="/js/src/scrollspy.js?v=5.1.2"></script>
<script type="text/javascript" src="/js/src/post-details.js?v=5.1.2"></script>



  


  <script type="text/javascript" src="/js/src/bootstrap.js?v=5.1.2"></script>



  


  




	





  





  






  

  <script type="text/javascript">
    // Popup Window;
    var isfetched = false;
    var isXml = true;
    // Search DB path;
    var search_path = "search.xml";
    if (search_path.length === 0) {
      search_path = "search.xml";
    } else if (/json$/i.test(search_path)) {
      isXml = false;
    }
    var path = "/" + search_path;
    // monitor main search box;

    var onPopupClose = function (e) {
      $('.popup').hide();
      $('#local-search-input').val('');
      $('.search-result-list').remove();
      $('#no-result').remove();
      $(".local-search-pop-overlay").remove();
      $('body').css('overflow', '');
    }

    function proceedsearch() {
      $("body")
        .append('<div class="search-popup-overlay local-search-pop-overlay"></div>')
        .css('overflow', 'hidden');
      $('.search-popup-overlay').click(onPopupClose);
      $('.popup').toggle();
      var $localSearchInput = $('#local-search-input');
      $localSearchInput.attr("autocapitalize", "none");
      $localSearchInput.attr("autocorrect", "off");
      $localSearchInput.focus();
    }

    // search function;
    var searchFunc = function(path, search_id, content_id) {
      'use strict';

      // start loading animation
      $("body")
        .append('<div class="search-popup-overlay local-search-pop-overlay">' +
          '<div id="search-loading-icon">' +
          '<i class="fa fa-spinner fa-pulse fa-5x fa-fw"></i>' +
          '</div>' +
          '</div>')
        .css('overflow', 'hidden');
      $("#search-loading-icon").css('margin', '20% auto 0 auto').css('text-align', 'center');

      $.ajax({
        url: path,
        dataType: isXml ? "xml" : "json",
        async: true,
        success: function(res) {
          // get the contents from search data
          isfetched = true;
          $('.popup').detach().appendTo('.header-inner');
          var datas = isXml ? $("entry", res).map(function() {
            return {
              title: $("title", this).text(),
              content: $("content",this).text(),
              url: $("url" , this).text()
            };
          }).get() : res;
          var input = document.getElementById(search_id);
          var resultContent = document.getElementById(content_id);
          var inputEventFunction = function() {
            var searchText = input.value.trim().toLowerCase();
            var keywords = searchText.split(/[\s\-]+/);
            if (keywords.length > 1) {
              keywords.push(searchText);
            }
            var resultItems = [];
            if (searchText.length > 0) {
              // perform local searching
              datas.forEach(function(data) {
                var isMatch = false;
                var hitCount = 0;
                var searchTextCount = 0;
                var title = data.title.trim();
                var titleInLowerCase = title.toLowerCase();
                var content = data.content.trim().replace(/<[^>]+>/g,"");
                var contentInLowerCase = content.toLowerCase();
                var articleUrl = decodeURIComponent(data.url);
                var indexOfTitle = [];
                var indexOfContent = [];
                // only match articles with not empty titles
                if(title != '') {
                  keywords.forEach(function(keyword) {
                    function getIndexByWord(word, text, caseSensitive) {
                      var wordLen = word.length;
                      if (wordLen === 0) {
                        return [];
                      }
                      var startPosition = 0, position = [], index = [];
                      if (!caseSensitive) {
                        text = text.toLowerCase();
                        word = word.toLowerCase();
                      }
                      while ((position = text.indexOf(word, startPosition)) > -1) {
                        index.push({position: position, word: word});
                        startPosition = position + wordLen;
                      }
                      return index;
                    }

                    indexOfTitle = indexOfTitle.concat(getIndexByWord(keyword, titleInLowerCase, false));
                    indexOfContent = indexOfContent.concat(getIndexByWord(keyword, contentInLowerCase, false));
                  });
                  if (indexOfTitle.length > 0 || indexOfContent.length > 0) {
                    isMatch = true;
                    hitCount = indexOfTitle.length + indexOfContent.length;
                  }
                }

                // show search results

                if (isMatch) {
                  // sort index by position of keyword

                  [indexOfTitle, indexOfContent].forEach(function (index) {
                    index.sort(function (itemLeft, itemRight) {
                      if (itemRight.position !== itemLeft.position) {
                        return itemRight.position - itemLeft.position;
                      } else {
                        return itemLeft.word.length - itemRight.word.length;
                      }
                    });
                  });

                  // merge hits into slices

                  function mergeIntoSlice(text, start, end, index) {
                    var item = index[index.length - 1];
                    var position = item.position;
                    var word = item.word;
                    var hits = [];
                    var searchTextCountInSlice = 0;
                    while (position + word.length <= end && index.length != 0) {
                      if (word === searchText) {
                        searchTextCountInSlice++;
                      }
                      hits.push({position: position, length: word.length});
                      var wordEnd = position + word.length;

                      // move to next position of hit

                      index.pop();
                      while (index.length != 0) {
                        item = index[index.length - 1];
                        position = item.position;
                        word = item.word;
                        if (wordEnd > position) {
                          index.pop();
                        } else {
                          break;
                        }
                      }
                    }
                    searchTextCount += searchTextCountInSlice;
                    return {
                      hits: hits,
                      start: start,
                      end: end,
                      searchTextCount: searchTextCountInSlice
                    };
                  }

                  var slicesOfTitle = [];
                  if (indexOfTitle.length != 0) {
                    slicesOfTitle.push(mergeIntoSlice(title, 0, title.length, indexOfTitle));
                  }

                  var slicesOfContent = [];
                  while (indexOfContent.length != 0) {
                    var item = indexOfContent[indexOfContent.length - 1];
                    var position = item.position;
                    var word = item.word;
                    // cut out 100 characters
                    var start = position - 20;
                    var end = position + 80;
                    if(start < 0){
                      start = 0;
                    }
                    if (end < position + word.length) {
                      end = position + word.length;
                    }
                    if(end > content.length){
                      end = content.length;
                    }
                    slicesOfContent.push(mergeIntoSlice(content, start, end, indexOfContent));
                  }

                  // sort slices in content by search text's count and hits' count

                  slicesOfContent.sort(function (sliceLeft, sliceRight) {
                    if (sliceLeft.searchTextCount !== sliceRight.searchTextCount) {
                      return sliceRight.searchTextCount - sliceLeft.searchTextCount;
                    } else if (sliceLeft.hits.length !== sliceRight.hits.length) {
                      return sliceRight.hits.length - sliceLeft.hits.length;
                    } else {
                      return sliceLeft.start - sliceRight.start;
                    }
                  });

                  // select top N slices in content

                  var upperBound = parseInt('1');
                  if (upperBound >= 0) {
                    slicesOfContent = slicesOfContent.slice(0, upperBound);
                  }

                  // highlight title and content

                  function highlightKeyword(text, slice) {
                    var result = '';
                    var prevEnd = slice.start;
                    slice.hits.forEach(function (hit) {
                      result += text.substring(prevEnd, hit.position);
                      var end = hit.position + hit.length;
                      result += '<b class="search-keyword">' + text.substring(hit.position, end) + '</b>';
                      prevEnd = end;
                    });
                    result += text.substring(prevEnd, slice.end);
                    return result;
                  }

                  var resultItem = '';

                  if (slicesOfTitle.length != 0) {
                    resultItem += "<li><a href='" + articleUrl + "' class='search-result-title'>" + highlightKeyword(title, slicesOfTitle[0]) + "</a>";
                  } else {
                    resultItem += "<li><a href='" + articleUrl + "' class='search-result-title'>" + title + "</a>";
                  }

                  slicesOfContent.forEach(function (slice) {
                    resultItem += "<a href='" + articleUrl + "'>" +
                      "<p class=\"search-result\">" + highlightKeyword(content, slice) +
                      "...</p>" + "</a>";
                  });

                  resultItem += "</li>";
                  resultItems.push({
                    item: resultItem,
                    searchTextCount: searchTextCount,
                    hitCount: hitCount,
                    id: resultItems.length
                  });
                }
              })
            };
            if (keywords.length === 1 && keywords[0] === "") {
              resultContent.innerHTML = '<div id="no-result"><i class="fa fa-search fa-5x" /></div>'
            } else if (resultItems.length === 0) {
              resultContent.innerHTML = '<div id="no-result"><i class="fa fa-frown-o fa-5x" /></div>'
            } else {
              resultItems.sort(function (resultLeft, resultRight) {
                if (resultLeft.searchTextCount !== resultRight.searchTextCount) {
                  return resultRight.searchTextCount - resultLeft.searchTextCount;
                } else if (resultLeft.hitCount !== resultRight.hitCount) {
                  return resultRight.hitCount - resultLeft.hitCount;
                } else {
                  return resultRight.id - resultLeft.id;
                }
              });
              var searchResultList = '<ul class=\"search-result-list\">';
              resultItems.forEach(function (result) {
                searchResultList += result.item;
              })
              searchResultList += "</ul>";
              resultContent.innerHTML = searchResultList;
            }
          }

          if ('auto' === 'auto') {
            input.addEventListener('input', inputEventFunction);
          } else {
            $('.search-icon').click(inputEventFunction);
            input.addEventListener('keypress', function (event) {
              if (event.keyCode === 13) {
                inputEventFunction();
              }
            });
          }

          // remove loading animation
          $(".local-search-pop-overlay").remove();
          $('body').css('overflow', '');

          proceedsearch();
        }
      });
    }

    // handle and trigger popup window;
    $('.popup-trigger').click(function(e) {
      e.stopPropagation();
      if (isfetched === false) {
        searchFunc(path, 'local-search-input', 'local-search-result');
      } else {
        proceedsearch();
      };
    });

    $('.popup-btn-close').click(onPopupClose);
    $('.popup').click(function(e){
      e.stopPropagation();
    });
    $(document).on('keyup', function (event) {
      var shouldDismissSearchPopup = event.which === 27 &&
        $('.search-popup').is(':visible');
      if (shouldDismissSearchPopup) {
        onPopupClose();
      }
    });
  </script>





  

  

  

  

  

  

</body>
</html>
